1. Field of the Invention
The present invention relates to a wireless communication system. More particularly, the present invention relates to an apparatus and a method for adaptively performing beam forming in a wireless communication system that uses a Super High Frequency (SHF) band.
2. Description of the Related Art
To meet continually increasing Radio Frequency (RF) data traffic demands, wireless communication systems are evolving so as to support higher data transmission rates. For example, an emphasis in the development of a 4th Generation (4G) wireless communication system is an improvement in spectral efficiency in order to increase a data transmission rate. However, it has become difficult to meet the continually increasing RF data traffic demands with only improvements in the spectral efficiency.
The above problem may alternatively be addressed by employing a wider frequency band. A frequency band used by a mobile communication system of the related art is typically 10 GHz or less. The reason for this is that it is very difficult to secure a wider frequency band at 10 GHz or less. However, a wider frequency band may be more easily secured in a super high frequency band (e.g., 30 GHz through 150 GHz). The super high frequency band may also be referred to as the millimeter (mm) wave band.
However, the use of the super high frequency band has a shortcoming in that as a frequency for wireless communication increases, a radio path loss increases. Accordingly, as the frequency for wireless communication increases, radio reach distance is correspondingly shortened, thereby resulting in a reduced service coverage area. However, there is a technique to address this shortcoming, namely beam-forming. Beam-forming addresses the radio path loss and increases the radio reach distance.
Beam-forming may be classified into a transmission beam-forming and a reception beam-forming. The transmission beam-forming concentrates a reach region of a radio wave in a specific direction. The reach region of a radio wave may be concentrated in a specific direction using a plurality of antennas. Generally, a structure including the plurality of antennas is referred to as an antenna array, and an individual antenna included in the antenna array is referred to as an array element. In a case where transmission beam-forming is applied, a transmission distance of a signal increases in an intended direction, and simultaneously, the transmission distance of the signal in directions other than the intended direction are minimized. Therefore, interference to other users located in directions other than the intended direction is reduced. In the reception beam-forming, a reception side concentrates reception of radio waves from a specific direction using a reception antenna array. Accordingly, strength of a signal received from an intended direction increases, and strength of a signal received from directions other than the intended direction are excluded, so that an interference signal from a direction other than the indented direction is effectively blocked.
As described above, in order to secure a wider frequency band, utilization of a super high frequency band, that is, a millimeter (mm) wave band, is expected. In this case, beam-forming may be employed to overcome a radio path loss. Therefore, techniques are desired for effectively performing beam-forming in a mobile communication environment where a user moves and a radio environment changes.